The present invention relates to computer telephony. More specifically, the present invention relates to a telecommunications interface for a computer that provides electrical power appropriate for telephony applications.
Present day analog telephone systems the United States typically rely upon standards set by Bellcore, the standards division of the former Bell Telephone Company. These exhaustive standards detail the magnitudes of a variety of telephone related signals, the periods of signals, the timings of signals, and the like. For example, these Bellcore standards specify a range of voltages necessary to power an analog telephone, a range for voltages necessary to ring a ringer of a telephone, methods for indicating when messages are waiting in a voice mail-type system, and the like. Many other such standards are also described, including the duration of a telephone ring, and the like.
In the past, typical private branch exchange (PBX) systems for large and small corporations included computer systems having proprietary switching hardware and proprietary control software. These traditional PBX systems were very costly in terms of hardware and software required, as well as very costly in terms of maintenance and service required. For example, traditional PBX systems typically range in cost of tens of thousands of dollars for a simple PBX system to hundreds of thousands of dollars for a large PBX and on up. Such PBX systems were thus very costly, especially for smaller to medium sized businesses.
Only recently has the personal computer become a viable hosting mechanism for telephony applications. This was due in part to the increased processing power of personal computers and the availability of more robust real-time multi-processing, multi-threaded operating systems. Other reasons for the paradigm shift to computer telephony was the introduction of dedicated computer plug-in boards and software that provided PBX switching functionality.
By providing relatively low cost hardware and open and maintainable software, in contrast to the traditional systems, the new computer telephony integration (CTI) model has drastically reduced the costs of PBXs systems. One of the pioneering companies in the field of computer telephony integration was AltiGen Communications AltiServ™ product.
One of the many challenges of combining telephony applications with personal computers was that typical computers generated a small number of output voltages for plug-in boards. For example, voltages on ISA, EISA, VESA, PCI, and the like buses typically include only +12 volts DC and +5 volts DC. In contrast, telephony applications, as specified by Bellcore standards, typically require telephone output signals such as −24 volts DC, −48 volts DC, −125 volts DC, 90 volts AC, and the like. Thus, for computer telephone integration to be successful, voltages appropriate for telephony had to be supplied to the plug-in boards.
One method for providing plug-in telephone server boards with power supply voltages appropriate for telephony has been to provide external power supplies to the plug-in boards. In such cases, the user would plug-in the telephone server into a computer chassis, plug in an external power supply into a wall socket, and then couple the external power supply to the telephone server in the computer. In such a case, the telephone server would rely upon power from the external power supply to provide operational power to the telephones, to provide ringing signals, and the like.
Drawbacks to such methods included that the user could be required to provide dedicated external power supplies for each plug-in board. Other drawbacks included that the external power supplies were typically off the shelf and provided more power capability than was needed. Further, in the case where the user wanted uninterrupted phone service, such methods required the user to get separate uninterrupted power supplies for the computer and for the external power supply.
Thus, in light of the above, what is needed in the industry are improved methods and apparatus for providing power necessary for computer telephony applications.